Within Indonesia, there are numerous volcanoes which are erupting or at a raised alert status,
such as Krakatau.
One other volcano within this group is Mount Dempo, which is one of the tallest volcanoes
on the island of Sumatra as it stands at 3,142 meters or 10,308 feet above sea level.
It has been at a raised alert level of 2 since January 7th of 2022.
This alert level meant that the volcano could produce a small eruption with little or no
warning, and such an eruption finally occurred on May 31st.
At 1:54 am local time, the volcano produced a small explosion.
This explosion was triggered by the interaction of shallow magma with underlying groundwater
and material in Dempo's crater lake.
The heat from the shallow molten rock heated the water, causing it to flash to steam.
This caused an immense amount of pressure to build, as steam takes up a greater space
than the same volume of liquid water.
Eventually this pressure became too great, causing the gasses to escape upwards and generating
a volcanic explosion in what is known as a phreatic eruption.
Small pyroclastic flows were generated by this eruption, which traveled several hundred
meters downslope, primarily to the northwest.
In total, the small eruptive sequence lasted only 239 seconds after which seismic activity
returned to normal levels.
Over the next hour, a dusting of ash fell within a 5 kilometer radius of Dempo's summit,
totaling a mere 0.5 to 1 millimeter in thickness.
What had just occurred was a classic example of a low end VEI 1 explosive eruption, which
ejected slightly more than 10,000 cubic meters of tephra.
It represented Dempo's first volcanic eruption since November 9th of 2017, and fell within
the typical nature of eruptions at this volcano which are generally very brief, lasting less
than 10 minutes.
So, will additional eruptive activity occur at this volcano?
What is the current exclusion zone?
This video will answer these two questions and discuss the recent eruption.
The Mount Dempo volcano is located on the southwest portion of the island of Sumatra
within Indonesia where it is 97 kilometers east-southeast of the city of Bengkulu.
All historical eruptions at Dempo have occurred within its crater lake, which is itself constructed
within a complex series of explosion craters.
These craters are built within an andesitic volcanic cone which is where Dempo's highest
point is.
There is a smaller peak to the southeast which represents a section of rim from a 5 kilometer
wide older caldera most likely of Pleistocene age.
Along with the active crater which has a low point to the north and northwest, the existing
caldera rim naturally funnels the majority of eruptive products in those two directions.
The lack of vegetation surrounding the crater lake is indicative of where pyroclastic flows
and superheated boulders of rock generally travel eruptions occur, with little or no
plant life in a 900 meter radius around the vent.
However, the main hazard this volcano poses is related to mudflows termed lahars.
When a phreatic eruption occurs in the crater lake, it ejects large volumes of ash and acidic
water which then quickly travels downslope via a series of drainages.
These acidic lahars can travel several kilometers distant, but since the majority of eruptions
are quite small only heavily effect drainages within a 2 kilometer radius of Dempo's summit.
As a result of Dempo's continuing volcanic unrest, an exclusion zone has been placed
around the volcano.
It extends 1 kilometer around the summit crater and extends to 2 kilometers towards the north
and west of the crater where superheated material is most likely to flow.
I would also recommended avoiding crossing any drainages to the north of the volcano
in a 5 kilometer radius due to potential encounters with unusually long distance lahars.
In the next several days, Dempo may produce more similarly sized phreatic explosions or
the eruption may already be over.
While 47% of its eruptions lasted less than 24 hours in duration, some of its eruptions
have lasted as long as 239 days.
These eruptions have all been characterized by intermittent phreatic explosions during
that timespan.
Thanks for watching!
If you would like to request a specific topic, please leave a comment below.
Additionally, I would like to thank my new patron Ben Thomas for supporting this channel!